The present invention relates to a process for adhesively bonding together the surfaces of objects such as resin, wood and metal parts, and is particularly concerned with novel procedure for carrying out such bonding using an open-cell sponge or foam carrier containing a curable resin.
The basic problem with handling all liquid adhesives that are formulated to cure at ambient temperature is that the adhesive resin must be mixed with its hardener, or catalyst, and quickly spread over the surfaces to be bonded and pressed together before the adhesive begins to gel, or before expiration of the working life period. The spreading methods may involve scrapers, paddles or sprinkler nozzles or other similar techniques that result in non-uniform deposits of adhesive and result in smearing liquid adhesive over areas that should not receive adhesive, including the floor. Currently used liquid, room temperature curing adhesive mixture must be "filled" or mixed with powders such as Cabosil mineral powder to control dripping, sagging or migration when deposited in thickness greater than about 0.015 inches. The adhesive mixing equipment used for intermittant bonding operations must be located in the immediate proximity of the bonding operation, such as inside the hold of an LNG marine tanker, where the cleanup of the equipment and spillage of ingredients is likely to contaminate other components of the insulation system.
Various composites or thermosetting resin laminates have been prepared employing a sheet having an open-cell structure and containing a curable thermosetting resin. Thus, U.S. Pat. 4,042,746 to Hofer discloses a composite structure comprising a rigid closed-cell foam core element to which is bonded an initially resilient open-cell foam material and a layer of a reinforcing material, wherein the sandwich is placed in a mold and a compression load is applied and excess resin is extruded outwardly from the open-cell foam and the resin is heat cured to bond the high strength reinforcing material to the rigid closed-cell core element. However, such a system is not applicable for bonding large amounts of reinforced foam material at ambient temperature, for example, for bonding fiber reinforced foam insulation blocks together to provide a foam insulation layer in a ship or tanker for transporting liquid natural gas at cryogenic temperatures, or for bonding such foam insulation blocks to the inner ship hull, at the ship site.
U.S. Pat. Nos. 3,915,783, to Goppel et al and 3,930,919 to Chant et al disclose processes for producing a thermosetting resin laminate comprising impregnating an open-cell sheet with a thermosetting resin, applying a fibrous reinforcing layer to at least one side of the impregnated sheet, compressing the foam sheet and reinforcing layers to the extent that resin is expelled from the sheet into the fibrous reinforcing layer, and curing the resin in the sheet and reinforcing layer by heat curing in a mold at elevated temperature.
U.S. Pat. No. 3,193,437 to Schafer et al has a similar disclosure relating to the production of molded laminated articles.
U.S. Pat. No. 3,193,441 to Schafer discloses a laminate article prepared by impregnating a thermosetting resinous composition in liquid form into a resilient sheet of flexible foamed polyurethane having open connected cells to substantially fill such cells with resin, the impregnated sheet of foamed polyurethane is compressed between molding plates, and the thermosetting resinous composition is heat cured to a hardened condition while the impregnated sheet of foamed polyurethane is maintained under compression.
U.S. Pat. No. 3,697,630 to Yoshino discloses bonding a resinous body in a cavity, which comprises outgassing and freezing a body of normally liquid uncured resinous material to form a voidfree body, fitting the frozen body into a cavity and thereafter thawing the frozen resinous material and curing same to provide a bond to the walls of the cavity.